Xu Shanjia

Millimeter wave microstrip array design with CRLH-TL as feeding line

Based on the advance phase shift characteristics of left-handed transmission line, a millimeter wave microstrip array with composite right/left-handed transmission line as feeding line has been presented here. By means of CRLH-TL, insertion phase shift of the patch in the series configuration has been removed and higher gain of the array can be achieved.

Location accuracy of multistatic radars (TR/sup n/) based on ranging information

In modern ECM and ECCM environment, bistatic and multistatic radar systems have drawn increasing interest in many applications. It is well known that the position of a stationary or moving target can be estimated from measurements of the arrival times, directions of arrival, or Doppler shifts of electromagnetic waves received at various sites. An analysis based on ranging information for the target location accuracy of multistatic radar, with one transmitter and n receivers (TR/sup n/), is presented. The reasonable constellation of the system without knowing the transmitter position parameters is discussed. The geometric dilution of precision (GDOP) of the radar in a constrained space is also given.

Analysis of dispersion characteristics of Groove guides with mode-matching method

Groove guide is widely recognized as one of the most promising millimeter wave transmission structures. In this paper, the mode-matching method is used to analyse the dispersion characteristics of single and asymmetrical double groove guides, and the unified formulae of Nth-order approximation dispersion equations are presented. Based on this analysis, a general program for calculating the dispersion characteristrics of single and asymmetrical double groove guides has been completed. Some comparisons between the results obtained by present method and published data show that very good agreement has been seen. The effectiveness and the reliability of the given formulae and program are thus verified.

Finite-element analysis of dispersion and loss characteristics of groove guide with arbitrary shapes

The dispersion and loss characteristics of groove guide with arbitrary shapes are analyzed with high-order finite element method. The effectiveness and the reliablity of the method are verified by the experiments and the results obtained by other methods. Groove guides with various groove shapes, such as rectangular, triangular, parabolic, elliptic and cosine functions, are investigated systematically. The calculating results show that the dispersion of groove guide with different groove shape is almost the same, however, the loss characteristics is rather different; among them, V-shape groove guide has the lowest loss which is about half of the rectangular one. All the curves and the data given in this paper can be used in designing elements and circuits of the groove guide.

An unmanned air vehicle (UAV) GPS location and navigation system

GPS enhances the ability of UAV system to control the air vehicle, an electronic map displays dynamically the position results and happenings around the UAV. To combine GPS and electronic map, visual UAV dynamic location and navigation is realized.

Improved perturbation analysis of millimeter-wave omni-directional periodic dielectric rod antenna

The characteristics of the omni-directional periodic circular dielectric rod leaky-wave antenna is analyzed by the improved perturbation method. The electromagnetic fields are described in terms of a radial transmission-line network, which brings considerable physical insight into the overall behavior of the periodic antenna. The analysis yields expression for the leakage constant in a closed form, and the design procedure of the antenna is tremendously simplified. Comparisons between the approximate and rigorous results, as well as the experiment data, are made. It is found that accuracy obtainable from the perturbation analysis is adequate for practical design purposes.

Performance analysis of the estimation of time delay and Doppler stretch by wideband ambiguity function

In this paper, the performance of estimation of time delay and Doppler stretch by the wideband ambiguity function method (WBAF) is investigated. The comparison between the present result and that of Qu Jin et al. (see IEEE Trans., vol. SP-43, no. 4, p. 904-16, 1995) shows that the present result is more exact. Then we propose a modified returned signal model, and using the model we evaluate the maximum likelihood estimation (MLE) performance of the time delay and Doppler stretch, which shows that when the phase angle of the reflection coefficient /spl phi//sub 0/ is known, the MLE performance is similar to the result given by Qu Jin et al. in the case that /spl phi//sub 0/ is unknown. The result also demonstrates that WBAF method is an asymptotically optimal one.

Improved perturbation analysis of dielectric grating antenna

An imptoved pepturbation procedure is used for analyzing the radiation characteristics of the millimeter wave dielectric grating antenna. The electromagnetic fields are described in terms of a transverse transmission line network, which brings considerable physical insight into the overall behavior of the antenna. The analysis is practical and yields as highly results as the rigorous method despite the simplicity of the present procedure.

Realization of quasi uniform left-handed medium based on LH transmission line

Derived from the dual equivalent circuit for LH materials, two left-handed (LH) transmission lines (TL) with a microstrip structure are presented. Both structures show the backward-wave radiation pattern as well as anti-parallel phase velocity with group velocity, which demonstrate the LH characteristics of the structures. Because of its compactness, the improved structure can be easily applied in MIC and MMIC design.

Scattering characteristics of 3-D discontinuity consisting of semiconductor sample filled in waveguide with gaps

The scattering characteristics of 3-D discontinuity consisting of II-VI-epitaxial layer grown on lossy dielectric substrate inserted in the waveguide with gaps are investigated in detail by the method which combines the multimode network theory with the rigorous mode matching procedure. The experimental data verify the accuracy and the effectiveness of the present method.